This invention relates to shock absorbers and more particularly to a shock absorber providing superior shock absorbing characteristics in an extremely compact package.
Shock absorbers which force fluid through a restricted orifice to convert the kinetic energy of a moving part into an increase of thermal energy of the fluid are commonly used on machines. The smoothest deceleration of the moving parts is obtained by absorbers which offer a constant resistive force to the motion over the total length of the deceleration.
One class of such devices employs a piston connected to the machine part and movable within a metering cylinder or tube having a closed end. A series of exponentially spaced orifices are formed along the length of the tube wall and the tube is supported within a housing filled with fluid. As the piston is forced into the tube by the motion of the machine part, the fluid is forced through the orifices and the kinetic energy of the part is converted into thermal energy of the fluid. As the piston moves down the metering tube it succcessively closes off the orifices so that the force imposed on the load is maintained relatively constant resulting in a substantially linear deceleration of the moving part.
The force imparted on the part is a function of the effective configuration of the fluid orifices, and shock absorbers of this class have been designed wherein an outer tube or sleeve fits over the inner, metering tube and is provided with metering means which coact with the metering orifices in the inner tube to vary the resistive force in response to relative movement between the tubes, thereby allowing the shock absorber to be selectively adjusted for use with parts having varying weights and kinetic energy.
Whereas these prior art shock absorbers have provided the desired substantially constant resistive force to the motion over the total period of the deceleration and have provided the desired ability to vary the resistance to accommodate parts having varying weights and kinetic energy, the prior art devices have offered this performance and adjustability at the expense of a rather large total package, which has had a limiting effect with respect to the usability of the shock absorbers in certain environments where space and/or weight are critical.